The microflora in deep periodontal pockets is predominantly gram negative rods. The antigenic relationships of these organisms is under investigation with emphasis on the vibrio-corroder group isolated at Forsyth Dental Clinic from patients with periodontal disease. The objective is to produce antisera which will identify these organisms on primary isolation and within tissues by use of indirect immunofluorescence (IFA). Microagglutination studies have shown that Eikenella corrodens sps., Bacteroides corrodens sps., anaerobic vibrios and Campylobacter-like organisms do not cross react antigenically. Wall antigens are being isolated which will allow identification of six serogroups of Eikenella. Available sera are in use to identify the isolates from periodontitis patients and excised gingival tissues will be studied by IFA for possible colonization by vibrio-corroders. High titre rat anti-Eikenella serum is in use to study the role of E. corrodens in the rabbit endocarditis model. Transfer of genetic information by conjungation and transformation is being studied in the vibri-corroder group. The ultimate objective is to gain a better understanding of the incidence and pathogenic potential of the vibrio-corroder group of organisms in periodontal disease.